Exchange/RJE Manual

The ACK 1 Character

BSC Line Control

C–2 104698 Tandem Computers Incorporated

An ACK 0 is transmitted as shown:

ASCII line code EBCDIC line code

pad pad

SYN SYN

DLE DLE

0 %H 70

pad pad

The ACK 1 Character The ACK 1 (affirmative acknowledgment 1) character is not used in the control state.

In the message state, ACK 1 is the positive response to receipt of an odd-numbered

block. It means that the last block was received and validated (the BCC calculated at

the receiving station agreed with the BCC transmitted with the block). The station

receiving the ACK 1 can transmit the next block of data. The ACK 1 character always

causes a line turnaround (the station receiving the ACK 1 transmits next).

An ACK 1 is transmitted as shown:

ASCII line code EBCDIC line code

pad pad

SYN SYN

DLE DLE

pad pad

The STX Character The STX (start of text) character is not used in the control state. In the message state,

the STX character precedes the text or data portion of a block. STX also ends the

heading portion of a block.

When the STX character begins a block (the block has no heading), the STX character is

transmitted as shown:

ASCII line code EBCDIC line code

pad pad

SYN SYN

STX STX

text text